Toprol-XL My sister is on Toprol, just started, so I was looking up side effects. Cough is one, by the way. Considered rare, however, it's still a listed side effect. FYI: my sister is 57. She is a somewhat tense person, but slim and takes care of herself. She is having a horrible time getting started on this med. I am urging her to get a second or even a third opinion about her options.